The present invention is directed toward systems for composting organic matter, and more particularly toward aerated static pile composting systems.
Composting systems are utilized to convert virtually any type of organic waste into usable soil or soil additives. The composting process therefore satisfies the dual environmental concerns of the safe disposal of organic waste and the generation of soil or soil additives for various horticultural applications.
Composting technology has developed in two general directions. The first family of composting methods is based upon composting organic matter in open air stacked piles. The alternative family of composting methods involves placing the organic matter in closed bins, silos or similar containers.
The composting process is primarily dependent upon the action of aerobic bacteria. The composting bacteria are most active within a somewhat limited range of oxygen, temperature and moisture contents. Therefore, the efficiency of the composting process can be enhanced by operator control of the oxygen content, temperature, and moisture content of a compost pile.
The parameters of the composting environment are not constant throughout the composting process. Bacteriological activity in a new composting pile which contains a great deal of free organic matter is much higher than the activity in an older, more nearly fully composted pile. This bacteriological activity can generate foul odors. The odor problem can therefore be acute when means are employed to enhance the composting environment and accelerate the composting process.
Closed bin composting technology has been developed to address the need to control the parameters of the composting environment and also control foul odors. Closed bin systems however, have a relatively high cost per volume of compost produced.
Certain methods have also been developed in the field of open pile composting to address the above concerns. One method, known as the turned windrow process, involves manually turning over and agitating the composting material in a windrow pile on a daily or near daily basis. This method effectively aerates the pile, but requires a great deal of labor, and also requires extra space for the maneuvering of equipment and the effective stacking and re-stacking of the agitated piles. The turned windrow process provides no means for odor control. Alternatively, a static pile can be directly aerated by a blower and air pipe system which forces air under positive air pressure through and out of the pile on a continuous basis. This method too can worsen the odor problem associated with composting.
Certain advantages are inherent in an aerated system which can provide both positive air pressure and negative air pressure to a compost pile. In particular, under negative air pressure, air and excess fluid can be withdrawn from a pile into a conduit which enhances the opportunity for moisture, temperature and odor control. One such system for compost aeration is described in Gauthier, U.S. Pat. No. 4,521,517. The Gauthier system involves a permanent underground aeration system which utilizes a non-reversible blower and air pipe dampering arrangement to aerate a single static pile. The damper arrangement allows the operator to selectively place the compost pile under positive or negative air pressure. In addition, the Gauthier system features perforated aeration pipes below the compost pile which allow moisture to be withdrawn from the pile if it is placed under negative air pressure. The Gauthier system provides no means for supplemental odor control. In addition, the Gauthier system is a permanent underground system which requires significant capital expenditure to install. Finally, each individual compost pile in a composting facility will require its own separate self-contained Gauthier system including separate pipes and separate blowers. The necessity for multiple blowers vastly increases the capital cost of a large scale composting site and increases the utility costs incurred in the operation of a composting system. Finally, there is no provision in the Gauthier system for one compost pile to be in fluid communication with another.
The problem of odor generation in an aerated static pile composting system is addressed by Allen, U.S. Pat. No. 6,099,613. The method described by Allen involves drawing air under negative air pressure through a static pile during the initial phase of composting which is the time when the pile is most biologically active and therefore generating the most odors. The air and fluid condensate withdrawn from a pile are then mixed with a second air and liquid to cool the withdrawn air and liquid. This mixture is passed through a biofilter or a wet scrubber to mineralize or otherwise eliminate odors.
The Allen method does effectively cause the accelerated composting of a large volume of organic material, while controlling the release of offensive odors. However, like the Gauthier system, the apparatus necessary to implement the Allen method must be installed permanently under an improved surface. In addition, one or more air blowers is required per compost pile to effectively implement the Allen method. These requirements significantly increase the installation cost of a composting facility and render it suitable only for permanent installations.
The present invention is directed toward overcoming one or more of the problems discussed above.
A portable composting system for reconfigurably controlling the airflow to and from a plurality of aerated static composting piles includes an air blower having an air intake and an air output. A suction manifold is attached in fluid communication with the air intake of the blower. A discharge manifold is attached in fluid communication with the air output of the blower. A plurality of pile manifolds are connected to the suction manifold and the discharge manifold by a manifold crossover. The manifold crossover includes a pair of dampers which allow the composting apparatus operator to independently select positive or negative air pressure for application to each pile manifold. Each pile manifold is operatively associated with an aerated static compost pile, by means of a series of flexible air lances attached in fluid communication with a pile manifold.
The suction manifold is also connected to a system drain. The discharge manifold is connected with a biofilter. In an alternative implementation of the portable and reconfigurable composting apparatus the biofilter may be a multiple stage biofilter. The suction manifold can also be connected to a noise reduction medium.
Organic matter can be composted with the portable and reconfigurable composting apparatus assembled as described herein by placing a volume of organic material into a plurality of static piles. The single system wide air blower operates in one direction throughout the composting process. By manipulation of the dampers incorporated in the manifold crossover, the operator can communicate each of a series of pile manifolds and associated aerated static composting piles with the blower intake or the blower output. Therefore, the operator can selectively and independently apply positive or negative air pressure to a series of piles. The air and fluid withdrawn from a static pile under negative air pressure will contain odor producing compounds. These odor producing compounds can be reduced or substantially eliminated by flowing the air and fluid withdrawn from a compost pile under negative air pressure through a biofilter. In the alternative, the air and fluid withdrawn from a pile which is producing odors can be forced under positive air pressure through another older pile which acts as a biofilter for the first pile. The operator may further vary the rate of withdraw of air and fluid from a pile under negative air pressure or the rate of the application of air to a pile under positive air pressure by manipulation of dampers associated with the suction and discharge manifolds.
The composting apparatus described above and the method of composting described above can be carried out in aerated static piles placed upon an unimproved surface. Composting will be more complete and accelerated if the organic matter in the piles is re-stacked at 10-20 day intervals.
The apparatus and method of the present invention provides for accelerated aerated static pile composting while controlling odors which are inherently generated in the composting process. The dual goals of lowered cost and portability are achieved in the present invention by the use of a novel dampering arrangement which allows each of a plurality of aerated static piles to be placed under positive or negative air pressure at the operator""s discretion while utilizing only a single non-reversible system wide air blower. Furthermore, no pavement or permanent installation is necessary to implement the present invention, which further reduces installation costs and enhances portability.